Curable silicone composition with reduced mold fouling

Abstract

A curable silicone composition comprising (A) an alkenyl-containing organopolysiloxane comprising (A-1) a dialkylpolysiloxane that has an average of at least two alkenyl groups in each molecule), and (A-2) an alkenyl-containing, resin-form organopolysiloxane that comprises the SiO4/2 unit, R12R2SiO1/2 unit, and R13SiO1/2 unit; (B) an organopolysiloxane that has an average of at least three silicon-bonded hydrogen atoms in each molecule, wherein component (B) is an organopolysiloxane comprising (B-1) an organopolysiloxane that contains at least 0.7 mass % silicon-bonded hydrogen and that comprises SiO4/2 units and HR32SiO1/2 units in a ratio ranging from 1.50 to 2.50 moles of HR32SiO1/2 units per 1 mole of SiO4/2 units, at 50 to 100 mass % of component (B), and (B-2) a straight-chain organopolysiloxane that contains at least 0.3 mass % silicon-bonded hydrogen, at 0 to 50 mass % of component (B); and (C) a hydrosilylation reaction catalyst.

1 . A curable silicone composition comprising
 (A) 100 mass parts of an alkenyl-containing organopolysiloxane comprising
 (A-1) a dialkylpolysiloxane that has an average of at least two alkenyl groups in each molecule and a viscosity at 25° C. of 5000 to 1,000,000 mPas, at from 20 mass % to not more than 60 mass % of component (A), and 
 (A-2) an alkenyl-containing, resin-form organopolysiloxane that comprises an SiO 4/2  unit, R 1   2 R 2 SiO 1/2  unit, and R 1   3 SiO 1/2  unit wherein R 1  is C 1-10  alkyl and R 2  is alkenyl, and that contains the alkenyl group in the range from at least 1 mass % to less than 3.5 mass %, at from 40 mass % to not more than 80 mass % of component (A); 
   (B) an organopolysiloxane that has an average of at least three silicon-bonded hydrogen atoms in each molecule wherein the silicon-bonded groups other than the silicon-bonded hydrogen are C 1-10  alkyl, in an amount that provides 1.2 to less than 2.2 moles silicon-bonded hydrogen in this component (B) per 1 mole of the total alkenyl in component (A),
 and contains at least 0.7 mass % silicon-bonded hydrogen and that comprises SiO 4/2  units and HR 3   2 SiO 1/2  units in a ratio ranging from 1.50 to 2.50 moles of HR 3   2 SiO 1/2  units per 1 mole of SiO 4/2  units wherein R 3  is C 1-10  alkyl; and 
   (C) a hydrosilylation reaction catalyst in a catalytic quantity.   
     
     
         2 . A cured silicone material provided by curing the curable silicone composition according to  claim 1 , wherein a parallel light transmittance at 25° C. measured in accordance with JIS K 7105 on 6 mm optical path length is at least 90%. 
     
     
         3 . The cured silicone material according to  claim 2 , which has a hardness measured using the type A durometer as specified in JIS K 6253 in the range from at least 30 to not more than 90, an elongation as specified in JIS K 6251 of at least 50%, and the parallel light transmittance at 200° C. of a value that is at least 99% of the parallel light transmittance at 25° C. 
     
     
         4 . The cured silicone material according to  claim 2 , wherein curing is performed at a temperature from 120 to 180° C. 
     
     
         5 . The cured silicone material according to  claim 2 , wherein the cured silicone material is in a form of a cured silicone layer, such cured silicone layer and a substrate forms a single article, and wherein the cured silicone layer is formed on the substrate by heating to cure the curable silicone composition according to  claim 1  at a temperature from 120 to 180° C. 
     
     
         6 . The cured silicone material according to  claim 2 , which has a hardness measured using the type A durometer as specified in JIS K 6253 in the range from at least 50 to not more than 90. 
     
     
         7 . The curable silicone composition according to  claim 1 , wherein (B) is in an amount that provides 1.5-2.0 moles silicon-bonded hydrogen per 1 mole of the total alkenyl in component (A). 
     
     
         8 . The curable silicone composition according to  claim 1 , further comprising an additional ingredient selected from the group consisting of: an inhibitor, a mold release agent, a filler, an adhesion promoter, a heat stabilizer, a flame retardant, a reactive diluent, an oxidation inhibitor, and a combination of any two or more thereof. 
     
     
         9 . The curable silicone composition according to  claim 1 , wherein the dialkylpolysiloxane (A-1) has a viscosity at 25° C. of 10,000 to 500,000 mPas. 
     
     
         10 . A method of forming a cured silicone material, the method comprising the step of heating a curable silicone composition comprising (A) 100 mass parts of an alkenyl-containing organopolysiloxane comprising
 (A-1) a dialkylpolysiloxane that has an average of at least two alkenyl groups in each molecule and a viscosity at 25° C. of 5000 to 1,000,000 mPas, at from 20 mass % to not more than 60 mass % of component (A), and   (A-2) an alkenyl-containing, resin-form organopolysiloxane that comprises the SiO 4/2  unit, R 1   2 SiO 1/2  unit, and R 1   3 SiO 1/2  unit wherein R 1  is C 1-10  alkyl and R 2  is alkenyl, and that contains the alkenyl group in the range from at least 1 mass % to less than 3.5 mass %, at from 40 mass % to not more than 80 mass % of component (A);   (B) an organopolysiloxane that has an average of at least three silicon-bonded hydrogen atoms in each molecule wherein the silicon-bonded groups other than the silicon-bonded hydrogen are C 1-10  alkyl, in an amount that provides 1.2 to less than 2.2 moles silicon-bonded hydrogen in this component per 1 mole of the total alkenyl in component (A),   and that contains at least 0.7 mass % silicon-bonded hydrogen and that comprises SiO 4/2  units and HR 3   2 SiO 1/2  units in a ratio ranging from 1.50 to 2.50 moles of HR 3   2 SiO 1/2  units per 1 mole of SiO 4/2  units wherein R 3  is C 1-10  alkyl, and   (B-2) a straight-chain organopolysiloxane that contains at least 0.3 mass % silicon-bonded hydrogen wherein the silicon-bonded groups other than the silicon-bonded hydrogen are C 1-10  alkyl, at 0 to 50 mass % of component (B); and   (C) a hydrosilylation reaction catalyst in a catalytic quantity   at a temperature from 120 to 180° C. to form a cured silicone material.   
     
     
         11 . The method of  claim 10  further comprising the step of coating a mold with the curable silicone composition of  claim 1 , wherein heating is done by heating the mold to cure the curable silicone composition. 
     
     
         12 . The method of  claim 11  further comprising the steps of removing the cured silicone composition from the mold, recoating the mold with the curable silicone composition without cleaning the mold, and curing the curable silicone composition to form a cured silicone material. 
     
     
         13 . The method of  claim 12 , wherein the sequentially repeated over 1000 times before the mold is cleaned or replaced. 
     
     
         14 . The method according to  claim 10  wherein, prior to the heating step, further comprising the step of coating a substrate with the curable silicone composition so that the cured silicone material is a cured silicone layer that, together with the substrate, forms a single article.